1. Field
The invention is within the broad field of exercise devices which simulate physical activities such as swimming, walking or running, and more particularly such machines which simulate the bodily motions of cross country skiing.
2. Prior Art
In cross country skiing, the legs move reciprocally forward and backward with respect to the body oppositely to each other. Backward leg motions provide the forward propulsive force, while forward leg motions place the associated skis into position for the next backward leg motion. A pair of ski poles, powered by arm, shoulder, back and chest muscles, provides additional forward thrust. The ski poles may be used in reciprocating motions similar to that of the skis or in simultaneous rearward thrusting motions followed by simultaneous forward movement of the poles to obtain purchase for the next rearward thrust. While a great number of machines have been devised to simulate downhill skiing, few have dealt with cross country skiing. U.S. Pat. No. 3,941,377 discloses a device with simulated ski segments 39 and 40 each provided with an underlying endless flexible belt tread allowing the skier to stride against frictional resistance provided to backward movement of the belt treads. The skis act against separate belts also frictionally restrained against rearward motion. The user therefore tends to move forward off the apparatus, restrained however by forward stops for the ski segments against which the skier must act. In U.S. Pat. No. 4,023,795, frictional resistance to backward ski motions are provided by friction wheels 21. In this design, an upright waist high pedestal must be provided in front of the skier, against which he is pressed during exercise to restrain him from moving fowardly off the device. Simulated ski poles are provided having a ground engaging frictionally attached disc to simulate resistance of ski pole strokes. The ski pole forward forces on the skier also press the skier against the restraining pedestal. The problem of restraining the skier is always attendant to devices employing such frictional restraint, and generally leads to undesirable complexity in the device. Also, body stops are unnatural and generally reduce the enjoyment in use of these devices.
Another friction utilizing device is disclosed in U.S. Pat. No. 4,023,795. Guided foot dollies are disclosed in U.S. Pat. Nos. 3,559,986 and 1,909,190. No connection between dollies is provided in U.S. Pat. No. 3,559,986, the skier being protected for excessively long, hard to control, foot separations only by end stops. It is complicated by pivotable foot contacting portions of the dollies. Guided dollies connected for reciprocatory parallel movement are disclosed in U.S. Pat. No. 1,909,190. These exercisers avoid some of the aforesaid disadvantages of the friction devices, but are not adapted for skiing simulation, having no simulated ski poles. While the arms and upper body are exercised considerably, many muscles used in cross country skiing remain unused. Further, they are not adapted for use by the infirm, considerable athletic ability, especially balancing capability, being needed in the absence of the poles or other graspable body support provision. The devices requiring lifting and setting down of the feet introduce impact shock into ankle and knee joints similarly to jogging, which may preclude their use by people with arthritis or other joint weaknesses.